Conventionally, there is known a balancer device which cancels a variation in gravitational torque generated by the rotation of a robot arm (see e.g., Patent Literature 1).
This balancer device couples a first arm to a base body. A rod end of a balancer is coupled to a fixed shaft protruding laterally of the first arm. The other end of the balancer which is closer to a cylinder is coupled to a fixed shaft provided at the lower portion of the base body. With this configuration, the rotation of the first arm is assisted.